🐛 fix(window): 加固 Windows 冷启动半窗，原生最大化并兜底铺满工作区

- Windows 启动 WindowStartState 改为 Maximised，默认尺寸提升到 1440×900
- 无记忆/历史 1024×768/覆盖率过低的普通窗记忆改为启动最大化
- Maximise 多次失败时铺满工作区兜底，避免残留浮动半窗
- 用户刻意拉大的普通窗仍先 Unmaximise 再恢复尺寸位置

frontend/src/utils/windowStartupLayout.test.ts

@@ -5,6 +5,9 @@ import {
   isStartupWindowRestorePending,
   markStartupWindowRestorePending,
   resolveDefaultStartupWindowBounds,
+  resolveWorkAreaFillWindowBounds,
+  shouldPreferWindowsStartupMaximise,
+  WINDOWS_STARTUP_MAXIMISE_AREA_RATIO,
 } from './windowStartupLayout';
 
 describe('windowStartupLayout', () => {
@@ -69,4 +72,61 @@ describe('windowStartupLayout', () => {
     vi.setSystemTime(new Date('2026-07-09T10:00:01.001Z'));
     expect(isStartupWindowRestorePending()).toBe(false);
   });
+
+  it('fills the OS work area as a maximise-failure fallback', () => {
+    expect(resolveWorkAreaFillWindowBounds({
+      availWidth: 1920,
+      availHeight: 1040,
+      availLeft: 0,
+      availTop: 0,
+    })).toEqual({
+      width: 1920,
+      height: 1040,
+      x: 0,
+      y: 0,
+    });
+
+    expect(resolveWorkAreaFillWindowBounds({
+      availWidth: 1600,
+      availHeight: 900,
+      availLeft: 1920,
+      availTop: 40,
+    })).toEqual({
+      width: 1600,
+      height: 900,
+      x: 1920,
+      y: 40,
+    });
+  });
+
+  it('prefers maximise for missing, legacy 1024×768, and undersized default windows', () => {
+    const viewport = {
+      availWidth: 1920,
+      availHeight: 1080,
+      availLeft: 0,
+      availTop: 0,
+    };
+
+    expect(shouldPreferWindowsStartupMaximise(null, viewport)).toBe(true);
+    expect(shouldPreferWindowsStartupMaximise({
+      width: 1024,
+      height: 768,
+      x: 0,
+      y: 0,
+    }, viewport)).toBe(true);
+
+    // 84%×84% default area ≈ 0.706 < 0.78 → 最大化
+    const defaultBounds = resolveDefaultStartupWindowBounds(viewport);
+    expect((defaultBounds.width * defaultBounds.height) / (1920 * 1080))
+      .toBeLessThan(WINDOWS_STARTUP_MAXIMISE_AREA_RATIO);
+    expect(shouldPreferWindowsStartupMaximise(defaultBounds, viewport)).toBe(true);
+
+    // 用户刻意拉大的普通窗应保留
+    expect(shouldPreferWindowsStartupMaximise({
+      width: 1760,
+      height: 980,
+      x: 80,
+      y: 40,
+    }, viewport)).toBe(false);
+  });
 });

frontend/src/utils/windowStartupLayout.ts

@@ -16,6 +16,16 @@ export type StartupWindowBounds = {
 const MIN_STARTUP_WIDTH = 900;
 const MIN_STARTUP_HEIGHT = 600;
 
+/**
+ * 工作区覆盖率低于该阈值时，视为「半窗 / 默认小窗」记忆，Windows 启动改走最大化。
+ * 84%×84% 居中默认窗的面积比约为 0.706，会被捕获；用户刻意拉大的普通窗通常更高。
+ */
+export const WINDOWS_STARTUP_MAXIMISE_AREA_RATIO = 0.78;
+
+/** Align with historical main.go Width/Height defaults that look half-open on modern screens. */
+const LEGACY_DEFAULT_WIDTH = 1024;
+const LEGACY_DEFAULT_HEIGHT = 768;
+
 /**
  * Resolve a usable first-launch window when no persisted bounds exist.
  * Windows defaults to top-left 1024x768 which looks "half open" on modern screens.
@@ -50,6 +60,62 @@ export const resolveDefaultStartupWindowBounds = (
   };
 };
 
+/**
+ * Fill the OS work area (taskbar excluded). Used when Maximise API fails on Windows
+ * so the shell still looks "full" instead of lingering at 1024×768 / 84% floating.
+ */
+export const resolveWorkAreaFillWindowBounds = (
+  viewport: StartupVisibleViewport,
+): StartupWindowBounds => {
+  const availWidth = Math.max(0, Math.trunc(Number(viewport.availWidth) || 0));
+  const availHeight = Math.max(0, Math.trunc(Number(viewport.availHeight) || 0));
+  const availLeft = Math.trunc(Number(viewport.availLeft) || 0);
+  const availTop = Math.trunc(Number(viewport.availTop) || 0);
+
+  if (availWidth <= 0 || availHeight <= 0) {
+    return resolveDefaultStartupWindowBounds(viewport);
+  }
+
+  return {
+    width: Math.max(MIN_STARTUP_WIDTH, availWidth),
+    height: Math.max(MIN_STARTUP_HEIGHT, availHeight),
+    x: availLeft,
+    y: availTop,
+  };
+};
+
+/**
+ * Decide whether Windows cold-start should prefer maximise over restoring bounds.
+ * - 无记忆 / 非法尺寸 → 最大化
+ * - 仍像旧默认 1024×768 → 最大化
+ * - 覆盖工作区面积过低（含历史 84% 居中默认窗）→ 最大化
+ */
+export const shouldPreferWindowsStartupMaximise = (
+  bounds: StartupWindowBounds | null | undefined,
+  viewport: StartupVisibleViewport,
+): boolean => {
+  if (!bounds) {
+    return true;
+  }
+  const width = Math.trunc(Number(bounds.width) || 0);
+  const height = Math.trunc(Number(bounds.height) || 0);
+  if (width < 400 || height < 300) {
+    return true;
+  }
+  if (width <= LEGACY_DEFAULT_WIDTH && height <= LEGACY_DEFAULT_HEIGHT) {
+    return true;
+  }
+
+  const availWidth = Math.max(0, Math.trunc(Number(viewport.availWidth) || 0));
+  const availHeight = Math.max(0, Math.trunc(Number(viewport.availHeight) || 0));
+  if (availWidth <= 0 || availHeight <= 0) {
+    return false;
+  }
+
+  const areaRatio = (width * height) / (availWidth * availHeight);
+  return areaRatio < WINDOWS_STARTUP_MAXIMISE_AREA_RATIO;
+};
+
 let startupWindowRestorePendingUntil = 0;
 
 /** Mark a short grace window while startup maximise/fullscreen is still settling. */